man2/sigsuspend.2

   1 .\" Copyright (c) 2005 Michael Kerrisk
   2 .\" based on earlier work by faith@cs.unc.edu and
   3 .\" Mike Battersby <mib@deakin.edu.au>
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  27 .\" 2005-09-15, mtk, Created new page by splitting off from sigaction.2
  28 .\"
  29 .TH SIGSUSPEND 2 2019-03-06 "Linux" "Linux Programmer's Manual"
  30 .SH NAME
  31 sigsuspend, rt_sigsuspend \- wait for a signal
  32 .SH SYNOPSIS
  33 .B #include <signal.h>
  34 .PP
  35 .BI "int sigsuspend(const sigset_t *" mask );
  36 .PP
  37 .in -4n
  38 Feature Test Macro Requirements for glibc (see
  39 .BR feature_test_macros (7)):
  40 .in
  41 .PP
  42 .ad l
  43 .BR sigsuspend ():
  44 _POSIX_C_SOURCE
  45 .ad b
  46 .SH DESCRIPTION
  47 .BR sigsuspend ()
  48 temporarily replaces the signal mask of the calling thread with the
  49 mask given by
  50 .I mask
  51 and then suspends the thread until delivery of a signal whose
  52 action is to invoke a signal handler or to terminate a process.
  53 .PP
  54 If the signal terminates the process, then
  55 .BR sigsuspend ()
  56 does not return.
  57 If the signal is caught, then
  58 .BR sigsuspend ()
  59 returns after the signal handler returns,
  60 and the signal mask is restored to the state before the call to
  61 .BR sigsuspend ().
  62 .PP
  63 It is not possible to block
  64 .B SIGKILL
  65 or
  66 .BR SIGSTOP ;
  67 specifying these signals in
  68 .IR mask ,
  69 has no effect on the thread's signal mask.
  70 .SH RETURN VALUE
  71 .BR sigsuspend ()
  72 always returns \-1, with
  73 .I errno
  74 set to indicate the error (normally,
  75 .BR EINTR ).
  76 .SH ERRORS
  77 .TP
  78 .B EFAULT
  79 .I mask
  80 points to memory which is not a valid part of the process address space.
  81 .TP
  82 .B EINTR
  83 The call was interrupted by a signal;
  84 .BR signal (7).
  85 .SH CONFORMING TO
  86 POSIX.1-2001, POSIX.1-2008.
  87 .SH NOTES
  88 .PP
  89 Normally,
  90 .BR sigsuspend ()
  91 is used in conjunction with
  92 .BR sigprocmask (2)
  93 in order to prevent delivery of a signal during the execution of a
  94 critical code section.
  95 The caller first blocks the signals with
  96 .BR sigprocmask (2).
  97 When the critical code has completed, the caller then waits for the
  98 signals by calling
  99 .BR sigsuspend ()
 100 with the signal mask that was returned by
 101 .BR sigprocmask (2)
 102 (in the
 103 .I oldset
 104 argument).
 105 .PP
 106 See
 107 .BR sigsetops (3)
 108 for details on manipulating signal sets.
 109 .\"
 110 .SS C library/kernel differences
 111 The original Linux system call was named
 112 .BR sigsuspend ().
 113 However, with the addition of real-time signals in Linux 2.2,
 114 the fixed-size, 32-bit
 115 .IR sigset_t
 116 type supported by that system call was no longer fit for purpose.
 117 Consequently, a new system call,
 118 .BR rt_sigsuspend (),
 119 was added to support an enlarged
 120 .IR sigset_t
 121 type.
 122 The new system call takes a second argument,
 123 .IR "size_t sigsetsize" ,
 124 which specifies the size in bytes of the signal set in
 125 .IR mask .
 126 This argument is currently required to have the value
 127 .IR sizeof(sigset_t)
 128 (or the error
 129 .B EINVAL
 130 results).
 131 The glibc
 132 .BR sigsuspend ()
 133 wrapper function hides these details from us, transparently calling
 134 .BR rt_sigsuspend ()
 135 when the kernel provides it.
 136 .\"
 137 .SH SEE ALSO
 138 .BR kill (2),
 139 .BR pause (2),
 140 .BR sigaction (2),
 141 .BR signal (2),
 142 .BR sigprocmask (2),
 143 .BR sigwaitinfo (2),
 144 .BR sigsetops (3),
 145 .BR sigwait (3),
 146 .BR signal (7)